This invention relates to automatic systems for removing objects on an assembly line or conveyor.
In the past, conveyor lines of many different types have been equipped with various means for removing conveyed objects which have been identified as potentially defective. The systems that actually accomplish removal from the line, known generally as "rejectors" take several forms. The simplest, the ram rejector, involves a fast pneumatic cylinder alongside the conveyor that unceremoniously punches the offending object directly off the main conveyor line. The bottling industry has generally favored a more controlled approach.
One of the more widely used rejection systems in bottling lines involves a rotary take off system. Star wheels or vacuum wheels have selectively actuatable grippers which redirect selected individual bottles from the main conveyor line onto a separate reject conveyor like a rail spur while returning unaffected bottles to the main line. Rotary rejection systems, while offering more positive bottle control, are expensive, complicated, and often require spacing the bottles on the line. In addition, rotary systems take up a lot of space on the conveyor line. Consequently, they are not only expensive but difficult to retrofit into existing lines.
Greater attention has been focussed on rejection systems by one particular advance in bottling technology, namely the refillable, reusable plastic bottle. In many countries, particularly in Europe and South America, refillable plastic bottles are now in everyday use. Of course, refillable glass bottles have long been in use world-wide. Reusable plastic bottles are naturally far lighter and less fragile than glass. They have one shortcoming, however, that has slowed more widespread introduction. One of the plastics most often used for beverage bottles, namely polyethylene terephthalate or "PET", has a tendency, shared by most plastics, to absorb, over time, certain organic compounds, some more readily than others, contained in the substances with which the plastic comes in contact. In containers made of PET, these absorbed compounds can be gradually desorbed into the product to a degree which can potentially affect the quality of the product, depending on the type of product and storage conditions as well as the compound.
In extremely rare instances of misuse, reusable bottles come back to the bottler in dubious condition requiring special attention. Prior to refilling, of course, the returned bottles are thoroughly scoured and inspected. However, until now, on-line detection of residual contaminants before or after washing, which would be desirable because of desorption, has not been practical.
In a recent fortuitous development, competent, high speed, computerized chemical detection equipment is now becoming available at reasonable cost for sampling the air itself inside the bottles to distinguish the chemical composition of residues, on the fly, by analyzing vapors given off by the contaminants, without even slowing the bottles on the conveyor. But the advantage of on-line detection would be squandered if there were no cost-efficient means available for efficient in-line removal of the rare problem bottles after they are detected. With bottling lines running at speeds of 400 bottles per minute and up, even if detection is possible, cost effective, retrofittable bottle rejection systems compatible with these line speeds have not come to the fore to do the second half of the job. Given the sheer size of the installed investment in bottling lines all around the world, as well as the clear superiority of plastic bottles as beverage containers from the bottlers' standpoint, an efficient, low cost rejector system, compatible with the new detection technology, and easily retrofitted on existing bottling lines, would surely be much in demand.